Genetic analysis of regions involved in replication and cadmium resistance of the plasmid pND302 from Lactococcus lactis

The 8.8-kb Lactococcus lactis plasmid pND302 encodes resistance to cadmium (Cd-R). Regions of pND302 involved in replication and Cd-R were subcloned and sequenced The replication region is localized on a 1.5-kb region and consists of an open reading frame (repB) preceded by a noncoding AT-rich sequence (on) which is highly homologous to lactococcal theta-type replicons. The Cd-R determinant is localized on a 2.9-kb region and encodes putative proteins similar to the Cd2+-specific P-type efflux ATPase (CadA) and the transcriptional regulatory repressor (CadC) identified in Staphylococcus aureus, Bacillus firmus, and Listeria monocytogenes. Similar Cd-R determinants were also detected by PCR in other Cd-R plasmids isolated from different L. lactis strains. (C) 1997 Academic Press.